Doctoral Dissertations

Abstract

"Depth distributions of the radiation damage in moderately to heavily ion bombarded silicon was obtained in the following manner: The electron spin resonance signal from an ion bombarded silicon target was measured. This ESR signal was proportional to the amount of amorphous silicon present in the target. A thin oxide of specified thickness was then grown on the surface of the target by anodic oxidation and subsequently stripped off in a HF etch. The depth of the stripped impression below the unoxidized surface was measured using a multibeam interferometer. The amorphous ESR signal was again measured, and the strip / measure process was continued until the total implanted layer was removed.

These remaining- after-each-strip ESR signa ls have been plotted versus depth removed. Depth distributions of this type were called remaining amorphous depth distributions. Such distributions have been obtained for a selected set of ion masses, ion energies, ion doses, and target temperatures which respectively ranged from (Li+ through Xe+), (20 to 200 keV), (6x1012 to 6x1016 ions/cm2), and (80°K to 298°K).

The experimental profiles were compared with integral profiles calculated from theoretical damage distributions. We found that in those cases where only a small amount of nonamorphous damage was present at the critical dose, the experimental profile was in agreement with the theoretical profile. In those cases where a large amount of nonamorphous damage was present, experimental profiles at higher doses were needed to complement the critical dose profile at selected depths. This set of profiles was then compared with the theoretical results. While the agreement between the experimental and theoretical depth distributions was generally fair to excellent, in some cases the theoretical depth distribution would have to be radically changed to fit the experimental result.

It was also possible to deduce the energy deposited into atomic processes (damage) per incident ion from the amorphous ESR signal at the critical dose, corrected to include the non-amorphous damage. To determine this energy, a procedure for calibrating the experimental results to the theoretical results was chosen. We found that the theoretical calculations greatly overestimated the energy deposited into damage for light incident ions.

Furthermore, the experimental results al so showed that nonlinearities in the buildup of amorphous ESR signal with ion dos e were caused by non-uniform structure in the damage distribution.

Finally, the experimental results were used to establish an upper limit for the critical energy density, i.e., the density of damage need ed to form a small volume of amorphous silicon. This maximum possible value for the critical energy density at low target temperatures, ~ 80°K, was (3.5 ±0.9) x 1023 eV/cm3. However, our best estimate for the critical energy density at low target temperatures was (2.4 ±0.6) x 1023 eV/cm3"-- Abstract, pp. ii-iii

Advisor(s)

Hale, Edward Boyd

Committee Member(s)

Adawi, I., 1930-
Sparlin, Don M., 1937-2024
Kohser, Ronald A.
Park, John T.

Department(s)

Physics

Degree Name

Ph. D. in Physics

Publisher

University of Missouri--Rolla

Publication Date

Fall 1980

Pagination

xiv, 282 pages

Note about bibliography

Includes bibliographical references (pages 240-243)

Rights

© 1980 Joseph Sadowski, All rights reserved.

Document Type

Dissertation - Open Access

File Type

text

Language

English

Thesis Number

T 4646

Print OCLC #

8671907

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